Ink jet recording material and its use

ABSTRACT

An improved ink jet recording material is disclosed. It comprises on the front side of a subbed polyester at least two ink-receiving layers based on polyvinyl alcohol with a top layer containing a cationic mordant, and on the back side a double layer one of which contains an electronically conductive polymer.

FIELD OF THE INVENTION

[0001] The present invention relates to a particular type of ink jetrecording material and its use in printing applications.

BACKGROUND OF THE INVENTION

[0002] In the majority of applications printing proceeds by pressurecontact of an ink-loaden printing form with an ink-receiving materialwhich is usually plain paper. The most frequently used impact printingtechnique is known as lithographic printing based on the selectiveacceptance of oleophilic ink on a suitable receptor.

[0003] In recent times however so-called non-impact printing systemshave replaced classical pressure-contact printing to some extent forspecific applications. A survey is given e.g. in the book “Principles ofNon Impact Printing” by Jerome L. Johnson (1986), Palatino Press,Irvine, Calif. 92715, USA.

[0004] Among non-impact printing techniques ink jet printing has becomea popular technique because of its simplicity, convenience and low cost.Especially in those instances where a limited edition of the printedmatter is needed ink jet printing has become a technology of choice. Arecent survey on progress and trends in ink jet printing technology isgiven by Hue P. Le in Journal of Imaging Science and Technology Vol. 42(1), January/February 1998.

[0005] In ink jet printing tiny drops of ink fluid are projecteddirectly onto an ink receptor surface without physical contact betweenthe printing device and the receptor. The printing device stores theprinting data electronically and controls a mechanism for ejecting thedrops image-wise. Printing is accomplished by moving the print headacross the paper or vice versa. Early patents on ink jet printersinclude U.S. Pat. Nos. 3,739,393, 3,805,273 and 3,891,121.

[0006] The jetting of the ink droplets can be performed in severaldifferent ways. In a first type of process a continuous droplet streamis created by applying a pressure wave pattern. This process is known ascontinuous ink jet printing. In a first embodiment the droplet stream isdivided into droplets that are electrostatically charged, deflected andrecollected, and into droplets that remain uncharged, continue their wayundeflected, and form the image. Alternatively, the charged deflectedstream forms the image and the uncharged undeflected jet is recollected.In this variant of continuous ink jet printing several jets aredeflected to a different degree and thus record the image(multideflection system)

[0007] According to a second process the ink droplets can be created “ondemand” (“DOD” or “drop on demand” method) whereby the printing deviceejects the droplets only when they are used in imaging on a receiverthereby avoiding the complexity of drop charging, deflection hardware,and ink recollection. In drop-on-demand the ink droplet can be formed bymeans of a pressure wave created by a mechanical motion of apiezoelectric transducer (so-called “piezo method”), or by means ofdiscrete thermal pushes (so-called “bubble jet” method, or “thermal jet”method).

[0008] Ink compositions for ink jet typically include followingingredients dyes or pigments, water and/or organic solvents, humectantssuch as glycols, detergents, thickeners, polymeric binders,preservatives, etc. It will be readily understood that the optimalcomposition of such an ink is dependent on the ink jetting method usedand on the nature of the substrate to be printed. The ink compositionscan be roughly divided in:

[0009] water based; the drying mechanism involves absorption,penetration and evaporation;

[0010] oil based; the drying involves absorption and penetration;

[0011] solvent based; the drying mechanism involves primarelyevaporation;

[0012] hot melt or phase change: the ink vehicle is liquid at theejection temperature but solid at room temperature; drying is replacedby solidification;

[0013] UV-curable; drying is replaced by polymerization.

[0014] It is known that the ink-receiving layers in ink-jet recordingelements must meet different stringent requirements:

[0015] The ink-receiving layer should have a high ink absorbingcapacity, so that the dots will not flow out and will not be expandedmore than is necessary to obtain a high optical density.

[0016] The ink-receiving layer should have a high ink absorbing speed(short ink drying time) so that the ink droplets will not feather ifsmeared immediately after applying.

[0017] The ink dots that are applied to the ink-receiving layer shouldbe substantially round in shape and smooth at their peripheries. The dotdiameter must be constant and accurately controlled.

[0018] The receiving layer must be readily wetted so that there is no“puddling”, i.e. coalescence of adjacent ink dots, and an earlierabsorbed ink drop should not show any “bleeding”, i.e. overlap withneighbouring or later placed dots, or non-printed areas.

[0019] Transparent ink-jet recording elements must have a low haze-valueand be excellent in transmittance properties.

[0020] After being printed the image must have a good resistanceregarding waterfastness, lightfastness, and good endurance under severeconditions of temperature and humidity.

[0021] The ink jet recording element may not show any curl or stickybehaviour if stacked before or after being printed.

[0022] The ink jet recording element must be able to move smoothlythrough different types of printers.

[0023] All these properties are often in a relation of trade-off. It isdifficult to satisfy them all at the same time.

[0024] It is known that the presence in the ink accepting layer ofabsorptive pigments such as silica, kaolin, talc, aluminum oxide,boehmite, etc. improve the absorption capacity, the obtainable colourdensity and the drying time. Many patent applications have describedthis effect for many different binder-systems. U.S. Pat. No. 3,357,846describes pigments such as kaolin, talc, bariet, TiO₂ used in starch andPVA. U.S. Pat. No. 3,889,270 describes silica in gelatin, PVA andcellulose. Pigments and particles have also been described in patentapplications including DE 2,925,769, GB 2,050,866, U.S. Pat. Nos.4,474,850, 4,547,405, 4,578,285, WO 88 06532, U.S. Pat. No. 4,849,286,EP 339604, EP 400681, EP 407881, EP 411638 and U.S. Pat. No. 5,045,864(non-exhaustive list).

[0025] These particulates are dispersed in various types of binders ofwhich the most common types such as gelatin, polyvinyl alcohol,polyvinyl pyrrolidone, and various types of cellulose derivatives. Theseconventional binders are mentioned in numerous patent documents.

[0026] It is further known to use various types of film-forming polymersto improve the waterfastness of the coated ink receiving layer byincreasing its adhesion to the support.

[0027] It is also known to improve the waterfastness of the finishedprinted image by the incorporation of cationic pigments or mordantingpolymers bearing cationic quaternary groups such as ammonium-,sulphonium and phosphonium groups. These polymers interact with mosttypical ink jet inks resulting in a better anchoring of the dye in thebinder. Typical examples of such descriptions are U.S. Pat. Nos.4,371,582, 4,575,465, 4,649,064, GB 2 210 071 and EP 423829.

[0028] Many of the described or commercialy available ink jet recordingmaterials suffer from one or more of the following deficiencies

[0029] sticking of front side to back side of the freshly manufacturedink jet recording element when rolled up as a web or, or when stackedafter being cut in formats;

[0030] attraction of dust of the ink jet printed material when it isused as a master for the exposure of a printing plate such as an offsetplate or a silk screen, or of a contact duplicating film; this is due totriboelectric differences;

[0031] insufficient sharpness of the printed dots;

[0032] insufficient resistance to feathering;

[0033] transport problems during printing;

[0034] a lack of sufficient density of full areas of the printed image;

[0035] migration of ink from the printed side to the back side duringoccasional rolling up of the film during printing;

[0036] lack of dimensional stability. This property is of extremeimportance when the printed images emanate from digitally storedinformation corresponding to more then one colour selection, and theprinted images are to be used as masters.

OBJECTS OF THE INVENTION

[0037] It is an object of the present invention to provide an ink jetrecording material, and methods for its use, which is improved forsticking, the attraction of dust, and transport problems.

[0038] It is a further object of the invention to provide an ink jetrecording element, and methods for its use, on which sharp dots can beprinted.

[0039] It is a further object of the invention to provide an ink jetrecording element, and methods for its use, which is improved fordimensional stability.

SUMMARY OF THE INVENTION

[0040] The above mentioned objects are realised by two differentembodiments.

[0041] According to a first embodiment, the objects of the presentinvention are realized by providing an ink jet recording materialcomprising a transparent polyester support, and on the front side ofsaid support a layer pack (A) of at least two ink-receiving layerscomprising a polyvinyl alcohol binder whereby the top layer of said packfurther comprises a cationic mordant and a spacing agent, and on theback side of said support a double layer pack (B) comprising, in order,a latex subbing layer containing an electronically conductive polymer,and a second backing layer containing a crosslinked hydrophilic binderand a spacing agent.

[0042] According to a second embodiment, the objects of the presentinvention are realized by providing an ink jet recording materialcomprising a transparent polyester support, and on the front side ofsaid support a layer pack (A) of at least two ink-receiving layerscomprising a polyvinyl alcohol binder whereby the top layer of said packfurther comprises a cationic mordant and a spacing agent, and on theback side of said support a double layer pack (B′) comprising, in order,a latex subbing layer and a second backing layer containing anelectronically conductive polymer and a spacing agent.

[0043] So the essential difference between the two embodiments is theposition of the incorporation of the electronically conductive polymer.

[0044] A most suitable electronically conductive polymer is apoly(3,4-ethylenedioxythiophene)/polystyrene sulphonate complex.

[0045] Methods describing the use of the disclosed materials as mastersfor the exposure of a lithographic printing plate precursor or a silkscreen are explicitly considered as belonging to the scope of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

[0046] The layer assemblage and the ingredients of the ink jet recordingmaterial of the present invention will now be explained in detail.

[0047] the ink-receiving layers

[0048] The ink-receiving layer assemblage is a multilayer packcontaining at least two layers, and more preferably three layers. Anessential ingredient of those layers is a polyvinyl alcohol (PVA)binder. This PVA can be an unmodified, partially or almost completelyhydrolized PVA, Commercially available unmodified PVA binders includee.g. MOWIOL, trade mark of Hoechst AG, POLYVIOL WX 48/20, trade mark ofWacker Co., or AIRVOL 230, trade mark of Air Products Co. On the otherhand it can be a modified PVA, e.g. a cationic PVA such as GOHSEFIMERK-210, trade mark of Nippon Goshei Co., or a silanol modified PVA, suchas POVAL R2105, POVAL R1130, and POVAL R3109 of Kuraray CO.

[0049] The PVA can be used as the sole binder or can be admixed withsmall amounts of other well-known hydrophilic binders such as cellulosicderivatives, gelatin, polyvinyl pyrrolidone, etc.

[0050] At least the top layer of the multilayer ink-receiving layer packfurther contains a cationic mordant and a spacing agent.

[0051] An example of a useful cationic mordant is a cationicpolyurethane, such as WITCOBOND 213, trade mark of Crompton Corp.

[0052] Other suitable cationic compounds are poly(diallyldialkylammoniumchloride) compounds, e.g. a poly(diallyldimethylammonium chloride) or,in short, a poly(dadmac) These compounds are commercially available fromseveral companies, e.g. Aldrich, Calgon, Clariant, BASF, EKA Chemicals,Nalco Italiana and Nippon Goshei.

[0053] Other useful cationic compounds include dadmac copolymers such ascopolymers with acrylamide; dimethylamine-epichlorohydrine copolymers,e.g. POLYFIX 700, trade name of Showa High Polymer Co.; other Polyfixgrades which could be used are POLYFIX 601, POLYFIX 301, POLYFIX 301A,POLYFIX 250WS, and POLYFIX 3000; NEOFIX E-117, trade name of NiccaChemical Co., a polyoxyalkylene polyamine dicyanodiamine; REDIFLOC 4150,trade name of EKA Chemicals, a polyamine; MADAME(methacrylatedimethylaminoethyl=dimethylaminoethyl methacrylate) orMADQUAT (methacryloxyethyltrimethylammonium chloride) modified polymers,e.g. ROHAGIT KL280, ROHAGIT 210, ROHAGIT SL144, PLEX 4739L, PLEX 3073from Röhm, DIAFLOC KP155 and other DIAFLOC products from Diafloc Co.,and BMB 1305 and other BMB products from EKA chemicals; cationicepichlorohydrin adducts such as POLYCUP 171 and POLYCUP 172, trade namesfrom Hercules Co.; from Cytec industries: CYPRO products, e.g. CYPRO514/515/516, SUPERFLOC 507/521/567; cationic cellulose derivatives suchas CELQUAT L-200, H-100, SC-240C, SC-230M, trade names of Starch &Chemical Co., and QUATRISOFT LM200, UCARE polymers JR125, JR400, LR400,JR30M, LR30M and UCARE polymer LK; fixing agents from Chukyo Europe:PALSET JK-512, PALSET JK512L, PALSET JK-182, PALSET JK-220, WSC-173,WSC-173L, PALSET JK-320, PALSET JK-320L and PALSET JK-350;polyethyleneimine and copolymers, e.g. LUPASOL, trade name of BASF AG;triethanolamine-titanium-chelate, e.g. TYZOR, trade name of Du Pont Co.;copolymers of vinylpyrrolidone such as VIVIPRINT 111, trade name of ISP,a methacrylamido propyl dimethylamine copolymer; withdimethylaminoethylmethacrylate such as COPOLYMER 845 and COPOLYMER 937,trade names of ISP; with vinylimidazole, e.g. LUVIQUAT CARE, LUVITEC73W, LUVITEC VPI55 K18P, LUVITEC VP155 K72W, LUVIQUAT FC905, LUVIQUATFC550, LUVIQUAT HM522, and SOKALAN HP56, all trade names of BASF AG;polyamidoamines, e.g. RETAMINOL and NADAVIN, trade marks of Bayer AG;and phosphonium compounds such as disclosed in EP 609930. Still othercationic compounds include cationic aluminum oxide, cationic boehmite,and poly(aluminumhydroxychloride) such as SYLOJET A200, trade name ofGrace Co. Still further cationic polymers include polyvinylamines, e.g.PVAM-0595B from Esprit Co., and cationic modified acrylics, e.g. ACRITRKW319SX, trade name of Tasei Chemical Industries, and RD134 from GooChemical.

[0054] The nature and concentration of the spacing agent present in thetop layer of the ink receiving pack must be chosen so that the bestcompromise between full area density and transparency of the non-printedareas is obtained. So advantageously the spacing agents are transparentbeads. Classes of useful spacing agents include following:

[0055] the spherical polymeric beads disclosed in U.S. Pat. No.4,861,818;

[0056] the alkali-soluble beads of U.S. Pat. No. 4,906,560 and EP 584407

[0057] the insoluble polymeric beads disclosed in EP 466982.

[0058] polymethylmethacrylate beads;

[0059] copolymers of methacrylic acid with methyl- or ethylmethacrylate;

[0060] TOSPEARL siloxane particles, trade name of Toshiba Co.

[0061] SEAHOSTAR polysiloxane-silica particles (e.g. type KE-P50), tradename of Nippon Shokubai Co.

[0062] CHEMIPEARL, spherical polymeric particles, marketed by MisuiPetrochemical Industries, Ltd.

[0063] A preferred spacing agent is polymethylmethacrylate orderivatives. A most useful derivative is acopoly(methylmethacrylate-stearylmethacrylate 98%/2%), stabilized bypoly(styrene-maleic acid, sodium salt). This compound is preferableincorporated in a coated layer as a gelatinous dispersion.

[0064] Apart from the ingredients essential to the invention theink-receiving layers may contain still other types of substances.

[0065] Preferably they contain one or more surfactants, which can bechosen from the numerous known classes of surfactants. Most suitable arecationic surfactants, including e.g. N-alkyl dimethyl ammonium chloride,palmityl trimethyl ammonium chloride, dodecyldimethylamine,tetradecyldimethylamine, ethoxylated alkyl guanidine-amine complex,oleamine hydroxypropyl bistrimonium chloride, oleyl imidazoline, stearylimidazoline, cocamine acetate, palmitamine, dihydroxyethylcocamine,cocotrimonium chloride, alkyl polyglycolether ammonium sulphate,ethoxylated oleamine, lauryl pyridinium chloride,N-oleyl-1,3-diaminopropane, stearamidopropyl dimethylamine lactate,coconut fatty amide, oleyl hydroxyethyl imidazoline, isostearylethylimidonium ethosulphate, lauramidopropyl PEG-dimoniumchloridephosphate, palmityl trimethylammonium chloride, andcetyltrimethylammonium bromide.

[0066] The ink-receiving layers may contain some minor amounts ofpigments to such extent that they do not affect disadvantageously thetransparency of the global ink jet recording element.

[0067] The pigment may be chosen from organic material such aspolystyrene, polymethylmethacrylate, silicones, urea-formaldehydecondensation polymers, polyesters and polyamides. In general however, itis an inorganic porous pigment, such as silica, talc, clay, koalin,diatomaceous earth, calcium carbonate, magnesium carbonate, aluminiumhydroxide, aluminium oxide, titanium oxide, zinc oxide, barium sulfate,calcium sulfate, zinc sulfide, satin white, boehmite andpseudo-boehmite.

[0068] The layers may also comprise a plasticizer such as ethyleneglycol, diethylene glycol, propylene glycol, polyethylene glycol,glycerol monomethylether, glycerol monochlorohydrin, ethylene carbonate,propylene carbonate, tetrachlorophthalic anhydride,tetrabromophthalicanhydride, urea phosphate, triphenylphosphate,glycerolmonostearate, propylene glycol monostearate, tetramethylenesulfone, n-methyl-2-pyrrolidone, n-vinyl-2-pyrrolidone.

[0069] the support, the subbing layers, the backing layers

[0070] The support of the ink jet recording material used in accordancewith the present invention is a transparent polyester support, e.g. apolyethylene terephthalate or polyethylene naphtalate. Polyethyleneterephthalate (PET) is the preferred support. This support is subbed onboth sides with a so-called latex subbing layer. An essential ingredientof this latex subbing layer is an adhesion promoting latex. A preferredclass of latex polymers for this purpose are vinylidenechloride-containing copolymers having carboxyl functional groups.Illustrative of such polymers are (1) copolymers of vinylidene chlorideand an unsaturated carboxylic acid such as acrylic or methacrylic acid,(2) copolymers of vinylidene chloride and a half ester of an unsaturatedcarboxylic acid such as the monomethylester of itaconic acid, (3)terpolymers of vinylidene chloride, itaconic acid and an alkyl acrylateor methacrylate such as ethyl acrylate or methyl methacrylate, and (4)terpolymers of vinylidene chloride, acrylonitrile or methacrylonitrileand an unsaturated carboxylic acid such as acrylic acid or methacrylicacid.

[0071] In a most preferred embodiment the latex polymer is co(vinylidenechloride-methyl acrylate-itaconic acid; 88%/10%/2%). This copolymer isprepared by emulsion polymerization using 0.5% MERSOLAT H (trade-mark ofBayer AG) as emulsifying agent. It is necessary to add extra surfactant,a so-called post-stabilizer, to the latex in order to assure a goodstability on storage. An excellent storage stability is obtained when 4%of ULTRAVON W, trade mark of Ciba-Geigy, or DOWFAX, trade mark of Dow,is used.

[0072] As a further preferred ingredient of the coating solution of thelatex subbing layer colloidal silica may be added. A preferred compoundis KIESELSOL 100F (trade-mark of Bayer AG), average particle size 25-30nm. The ratio of the amount of latex to silica is preferably about80/20.

[0073] The latex subbing layer may further contain surfactants andbiocides.

[0074] It is an essential feature of the first embodiment of the presentinvention that the latex subbing layer of the back side of the supportfurther contains an electronically conductive polymer. Substances havingelectronic conductivity instead of ionic conductivity have aconductivity independent from moisture. They are particularly suited foruse in the production of antistatic layers with permanent andreproducible conductivity.

[0075] Many of the known electronically conductive polymers are highlycoloured which makes them less suited for use in films used for colourseparation, but some of them of the group of the polyarenemethylidenes,e.g. polythiophenes and polyisothianaphthene are not prohibitivelycoloured and transparent, at least when coated in thin layers. As aresult polythiophene derivatives are a preferred type of conductivecompounds for use in the present invention.

[0076] The production of conductive polythiophenes is described inpreparation literature mentioned in the above mentioned book “Scienceand Applications of Conducting Polymers”, p. 92.

[0077] For ecological reasons the coating of antistatic layers shouldproceed where possible from aqueous solutions by using as few aspossible organic solvents. The production of antistatic coatings fromaqueous coating compositions being dispersions of polythiophenes in thepresence of polyanions is described in EP 0 440 957. Thanks to thepresence of the polyanion the polythiophene compound is kept indispersion.

[0078] Preferably said polythiophene has thiophene nuclei substitutedwith at least one alkoxy group, or —O(CH₂CH₂O)_(n)CH₃ group, n being 1to 4, or, most preferably, thiophene nuclei that are ring closed overtwo oxygen atoms with an alkylene group including such group insubstituted form.

[0079] Preferred polythiophenes for use according to the presentinvention are made up of structural units corresponding to the followinggeneral formula:

[0080] in which:

[0081] each of R¹ and R² independently represents hydrogen or a C₁₋₄alkyl group or together represent an optionally substituted C₁₋₄alkylene group or a cycloalkylene group, preferably an ethylene group,an optionally alkyl-substituted methylene group, an optionally C-₁₋₂alkyl- or phenyl-substituted 1,2-ethylene group, a 1,3-propylene groupor a 1,2-cyclohexylene group.

[0082] The most preferred compound is poly(3,4-ethylenedioxy-thiophene),(PEDT) with following formula:

[0083] The preparation of said polythiophene and of aqueouspolythio-phene-polymeric polyanion dispersions containing saidpolythiophene is described in EP 0 440 957, cited above.

[0084] Suitable polymeric polyanion compounds required for keeping saidpolythiophenes in dispersion are provided by acidic polymers in freeacid or neutralized form. The acidic polymers are preferably polymericsulphonic acids. Examples of such polymeric acids are polymerscontaining vinyl sulfonic acid and styrene sulfonic acid or mixturesthereof.

[0085] The anionic acidic polymers used in conjunction with thedispersed polythiophene polymer have preferably a content of anionicgroups of more than 2% by weight with respect to said polymer compoundsto ensure sufficient stability of the dispersion. Suitable acidicpolymers or corresponding salts are described e.g. in DE-A-25 42 230,DE-A-25 41 274, DE-A-28 35 856, EP-A-14 921, EP-A-69 671, EP-A-130 115,U.S. Pat. Nos. 4,147,550, 4,388,403 and 5,006,451.

[0086] The weight ratio of polythiophene polymer to polymeric polyanioncompound(s) can vary widely, for example from about 50/50 to 15/85.

[0087] The most preferred polymeric polyanion for use in combinationwith the polythiophene derivative, e.g. PEDT, is polystyrene sulphonate(PSS).

[0088] Although a polythiophene/polyanion complex is the preferredelectronically conductive substance others can be used, e.g.polypyroles, polyanilines, sulphonated poly-p.-phenylenes, sulphonatedpolyfluorenes, polyphenylenevinylenes which can be carboxylated orsulphonated, polythienylenevinylenes which can be sulphonated orcarboxylated. Optionally these polymers can also be used as complex witha polymeric polyanion, e.g. polystyrene sulphonate.

[0089] In the first embodiment of the present invention the layer pack(B) on the back side comprises, apart from the latex subbing layer withthe conductive compound, a second backing layer comprising a crosslinkedhydrophilic binder and a spacing agent.

[0090] In a preferred embodiment the hydrophilic binder of the secondbacking layer is gelatin. Appropriate crosslinkers (or hardeners)include those of the epoxide type, those of the ethylenimine type, thoseof the vinylsulfone type, e.g.1,3-vinylsulphonyl-2-propanol, chromiumsalts e.g. chromium acetate and chromium alum, aldehydes e.g.formaldehyde, glyoxal, and glutaraldehyde, N-methylol compounds e.g.dimethylolurea and methyloldimethylhydantoin, dioxan derivatives e.g.2,3-dihydroxy-dioxan, active vinyl compounds e.g.1,3,5-triacryloyl-hexahydro-s-triazine, active halogen compounds e.g.2,4-dichloro-6-hydroxy-s-triazine, and mucohalogenic acids e.g.mucochloric acid and mucophenoxychloric acid. These hardeners can beused alone or in combination. The gelatin can also be hardened withfast-reacting hardeners such as carbamoylpyridinium salts as disclosedin U.S. Pat. No. 4,063,952. In a preferred embodiment the hardener is avinylsulfone.

[0091] The second backing layer further contains a spacing agent. Thisspacing agent may be chosen from the same types as described for the toplayer of the ink receiving layers. A most suitable compound is againcopoly(methylmethacrylate-stearylmethacrylate 98%/2%), stabilized bypoly(styrene-maleic acid, sodium salt). This compound is preferableincorporated in the second backing layer as a gelatinous dispersion.

[0092] In a second embodiment of the present invention the layer pack(B′) on the back side of the polyester support comprises a latex subbinglayer closest to the support, and an electroconductive layer as secondbacking layer. In this embodiment the latex subbing layer preferablycontains no or substantially no electronically conductive compound.Furtheron the composition is similar to the one described for the latexsubbing layer of the first embodiment. In the second embodiment theelectronically conductive compound is present in the second backinglayer. This electronically conductive compound is preferably chosen fromthe same compounds as decribed above for the first embodiment. A mostsuitable compound is again thepoly(3,4-ethylenedioxythiophene/polystyrene sulphonate complex. Thelayer further contains a spacing agent which again is preferably chosenfrom the classes described above. A most suitable compound is againcopoly(methylmethacrylate-stearylmethacrylate 98%/2%), stabilized bypoly(styrene-maleic acid, sodium salt). The binder of this backing layermay be hydrophilic or hydrophobic and may be crosslinked or not. Apreferred binder is a film-forming polymethylmethacrylate. Furtheronthis layer may contain other additives such as biocides and surfactants.

[0093] The latex subbing layer on the front side of the polyestersupport has preferably essentially the same composition as the latexsubbing layer of the back side, preferably however without the presenceof an electronically conductive polymer.

[0094] Furtheron on the front side there is also a so-called gelatinsubbing layer between the latex subbing layer and the ink-receivinglayers. In a preferred embodiment this gelatin subbing layer contains amixture of gelatin and colloidal silica. A preferred compound is againKIESELSOL 300F (trade-mark of Bayer AG). A plasticizing compound can beused in order to avoid the formation of cracks in the dried layer due tothe occurence of excessive shrinking of the layer during drying.Plasticizing agents are well-known in the art. Low-molecular weightcompounds (e.g. acetamide, glycerin) as well as polymeric latices (e.g.polyethylacrylate, poly-n.-butylacrylate) can be used for this purpose.Furtheron the gelatin subbing layer may contain one or more surfactants.Useful surfactants include: ULTRAVON™ W, an aryl sulfonate fromCIBA-GEIGY, DOWFAX from Dow CO., and ARKOPAL™ N060 (previously HOSTAPAL™W); a nonylphenylpolyethylene-glycol from HOECHST.

[0095] The thickness of the gelatin subbing layer is preferablycomprised between 0.1 and 1 μm.

[0096] coating technology

[0097] In a particularly preferred embodiment the two latex subbinglayers, the gelatin subbing layer, and the second backing layer arecoated “on line” in a continuous process in the manufacturing alley ofthe polyester itself. Molten polyester is extruded and longitudinallystretched. Then the first latex subbing layer is applied on the upperside and the second latex subbing layer, optionally conductive, isapplied on the back side. Then the subbed polyester is stretched in thetransversal direction. The gelatin subbing layer is applied on the upperside, and finally the second backing layer is applied on the back side.

[0098] The ink-receiving layers are coated “off-line”. Any well-knowncoating technique can be used such as dip coating, air-knife coating,slide hopper coating, and curtain coating.

[0099] use of ink jet image as master in printing processes.

[0100] An ink jet image produced image-wise from digitally storedinformation can be used as master for the exposure of a lithographicprinting plate. The method involves the following steps, in order,:

[0101] (1) preparing an ink jet recording material according to thepresent invention as explained above,

[0102] (2) jetting information-wise droplets of an UV-absorbing ink ontothe front surface of said ink jet recording material by means of an inkjet printer thus forming a printed image,

[0103] (3) exposing overall by actinic light a lithographic printingplate precursor through a mask consisting of the printed image formed bysteps (1) and (2),

[0104] (4) developing the exposed lithographic printing plate precursorinto a lithographic printing plate.

[0105] The ink used for the formation of the image may be any type ofink. Preferred however are aqueous inks. The UV absorbing colorant ofthe ink is preferably carbon black, but in principle also a mixture ofdyes adding up to black can be used provided that the UV density issufficient.

[0106] Multicolour printing can be performed by exposing severalprinting plates through different ink jet mask produced from digitalinformation corresponding to different colour separations. Thisapplication illustrates the importance of the dimensional stability ofthe ink jet material of the present invention.

[0107] Similarly, the ink jet image can be used as mask for the exposureof a silk screen. The method involves the following steps, in order,:

[0108] (1) preparing an ink jet recording material according to thepresent invention as explained above,

[0109] (2) jetting information-wise droplets of an ink absorbing inkonto the front surface of said ink jet recording material by means of anink jet printer thus forming a printed image,

[0110] (3) exposing overall by actinic light a silk screen through amask consisting of the printed image formed by steps (1) and (2),

[0111] (4) developing the exposed silk screen into a silk screenprinting element.

[0112] Similarly, multicolour printing or printing with different spotcolours, e.g. on textile fabrics, is possible.

[0113] The invention will now be illustrated by the following exampleswithout however being limited thereto.

EXAMPLES Example 1

[0114] 1.1 Composition of Invention and of Comparison Materials

[0115] composition of invention 1 material according to the firstembodiment:

[0116] On the front side of a PET support there were coated threeink-receiving layers having polyvinyl alcohol (MOWIOL) as binder. Thetop layer further comprises a polyurethane having cationic groups(WITCOBOND) and as spacing agentcopoly(methylmethacrylate-stearylmethacrylate 98%/2%), stabilized bypoly(styrene-maleic acid, sodium salt). Between the ink-receiving layerpack and the PET there were coated on line a latex subbing layercontaining essentially as adhesive latex co(vinylidene chloride-methylacrylate-itaconic acid; 88%/10%/2%), colloidal silica and surfactants,and a gelatin subbing layer containing essentially gelatin and colloidalsilica.

[0117] The first backing layer is an electroconductive latex subbinglayer comprising as adhesive latex co(vinylidene chloride-methylacrylate-itaconic acid; 88%/10%/2%), andpoly(3,4-ethylenedioxythiophene)/polystyrene sulphonate complex asconductive polymer. Further it contains colloidal silica (KIESELSOL100F), a surfactant and a biocide. The second backing layer comprisesgelatin crosslinked by a divinylsulfon hardener, and as matting agent agelatinous dispersion of copoly(methylmethacrylate-stearylmethacrylate98%/2%), stabilized by poly(styrene-maleic acid, sodium salt).

[0118] composition of invention 2 material according to the secondembodiment

[0119] The front side composition is the same as for the invention 1material. The first backing layer is a latex subbing layer similar tothe one of example 1.1 but without electronically conductive compound.The second backing layer comprisespoly(3,4-ethylenedioxythiophene)/polystyrene sulphonate complex asconductive polymer, copoly(methylmethacrylate-stearylmethacrylate98%/2%), stabilized by poly(styrene-maleic acid, sodium salt) as spacingagent, colloidal silica, a polyethylene emulsion, and film-formingpolymethylmethacrylate as binder.

[0120] comparison materials:

[0121] comparison 1: AJM CLEAR FILM, a commercially available material,marketed by Agfa-Gevaert, a material based on a gelatin/polyvinylpyrrolidone binder mixture on both sides.

[0122] comparison 2: Epson Transparant (S041063), a commercialtransparent material (microporous, based on boehmite)

[0123] 1.2 Evaluation of Physical Properties

[0124] 1.2.1 average dot size on an Epson 3000 printer

[0125] invention 1 material: 62 μm,

[0126] comparison 2 material: 74.5 μm.

[0127] 1.2.1 Tests on Sticking

[0128] The printed front sides of the invention and comparison materialswere after 10 minutes of drying pressed against different back layerpacks and kept so for 24 hours.

[0129] The tested back layer packs were the back layer packs of theinvention 1 material, of the invention 2 material and of the comparison1 material.

[0130] The printed front side of comparison material 1 sticked to alltested backsides and there was ink tranfer from front to back. Theprinted front side of invention material 1 only sticked to the back sideof comparison material 1 but not to the backsides of invention materials1 and 2, and there was no ink transfer.

[0131] 1.2.3 Printed Full Area Density

[0132] On an Epson 9000 printer (medium quality, normal dot) Invention 1material: visual density 3.44; UV density 2.81 Comparison 1 material:visual density 2.54; UV density 2.18

[0133]1.2.4 Wipe Tests

[0134] Freshly printed full areas were wiped in function of time with alittle stick having a tip of cotton-wool. Invention material 1 wasresistant to wiping after 1 á 2 minutes, while this was the case after 5minutes for comparison material 1.

[0135] 1.2.5 Dimensional Stability Tests

[0136] In following table 1 the dimensional stability values areexpressed as μm/m (reversible RV coefficients). The measurements wereperformed on samples cut both in the length and in the width direction.TABLE 1 Sample Dim. St. length Dim. St. width Mean value Inv. 1 13.513.2 13.4 Inv. 2 12.8 12.6 12.7 Comp. 1 23.4 22.8 23.1

Example 2

[0137] Comparison of Different Cationic Mordants

[0138] Samples were coated with similar composition as invention sample1 from the previous example with the exception that the nature of thecationic mordant was varied.

[0139] Following compounds were tested

[0140] cationic polyurethane dispersions: WITCOBOND 213 (cf. previousexample), ENOREX PU750, ENOREX PU950 (trade names of Collano Co.),CHROMOELASTIC C-4480 (trade name of Chromogenia-Units SA, Italy);

[0141] poly(dadmac) varianten: CAT FLOC 71259, CAT FLOC CFL, CATFLOC CL(trade names of Nalco Italiana S.r.l., Italy);

[0142] copolymers of dimethylamine and epichlorohydrine: REDIFLOC 4150(trade name of EKA Chemicals) and POLYFIX 601 (trade name of Showa HighPolymer Co.).

[0143] General Test Results

[0144] all samples showed a comparable good density and dot size;

[0145] the polyurethanes were better for drying characteristics;

[0146] the image quality was also the best for the polyurethanes.

1. An ink jet recording material comprising a transparent polyestersupport, and on the front side of said support a layer pack (A)comprising a latex subbing layer, a gelatin subbing layer, and at leasttwo ink-receiving layers comprising a polyvinyl alcohol binder wherebythe top layer of said ink-receiving layers further comprises a cationicmordant and a spacing agent, and on the back side of said support adouble layer pack (B) comprising, in order, a latex subbing layercontaining an electronically conductive polymer, and a second backinglayer containing a crosslinked hydrophilic binder and a spacing agent.2. An ink jet recording material according to claim 1 wherein saidcationic mordant is a cationic polyurethane latex.
 3. An ink jetrecording material according to claim 1 wherein said cationic mordant isa poly(diallyldialkylammonium chloride).
 4. An ink jet recordingmaterial according to claim 1 wherein said spacing agent in said topink-recording layer on the front side, and/or in said second backinglayer is copoly(methylmethacrylate-stearylmethacrylate 98%/2%),stabilized by poly(styrene-maleic acid, sodium salt).
 5. An ink jetrecording material according to claim 1 wherein said layer pack (A) onthe front side comprises three layers.
 6. An ink jet recording materialaccording to claim 1 wherein said electronically conductive polymer insaid latex subbing layer on the back side is a polythiophene/polyanioncomplex.
 7. An ink jet recording material according to claim 6 whereinsaid polythiophene is poly (3,4-ethylenedioxythiophene).
 8. An ink jetrecording material according to claim 6 wherein said polyanion ispolystyrene sulphonate.
 9. An ink jet recording material according toclaim 1 wherein said hydrophilic binder of said second backing layer isgelatin.
 10. An ink jet recording material according to claim 9 whereinsaid gelatin is crosslinked by means of a vinylsulfone hardener.
 11. Anink jet recording material comprising a transparent polyester support,and on the front side of said support a layer pack (A) comprising alatex subbing layer, a gelatin subbing layer, and at least twoink-receiving layers comprising a polyvinyl alcohol binder whereby thetop layer of said ink-receiving layers further comprises a cationicmordant and a spacing agent, and on the back side of said support adouble layer pack (B′) comprising, in order, a latex subbing layer and asecond backing layer containing an electronically conductive polymer anda spacing agent.
 12. An ink jet recording material according to claim 11wherein said cationic mordant is a cationic polyurethane latex.
 13. Anink jet recording material according to claim 11 wherein said cationicmordant is a poly(diallyldialkylammonium chloride).
 14. An ink jetrecording material according to claim 11 wherein said spacing agent insaid top ink-recording layer on the front side, and/or in said secondbacking layer is copoly(methylmethacrylate-stearylmethacrylate 98%/2%),stabilized by poly(styrene-maleic acid, sodium salt).
 15. An ink jetrecording material according to claim 11 wherein said layer pack (A) onthe front side comprises three layers.
 16. An ink jet recording materialaccording to claim 11 wherein said electronically conductive polymer insaid second backing layer is a polythiophene/polyanion complex.
 17. Anink jet recording material according to claim 16 wherein saidpolythiophene is poly(3,4-ethylenedioxythiophene).
 18. An ink jetrecording material according to claim 16 wherein said polyanion ispolystyrene sulphonate.
 19. A method for the preparation of alithographic printing plate involving the following steps, in order: (1)preparing an ink jet recording material as defined by any of claims 1 to18, (2) jetting information-wise droplets of a UV-absorbing ink onto thefront surface of said ink jet recording material by means of an ink jetprinter thus forming a printed image, (3) exposing overall by actiniclight a lithographic printing plate precursor through a mask consistingof the printed image formed by steps (1) and (2), (4) developing theexposed lithographic printing plate precursor into a lithographicprinting plate.
 20. A method according to claim 19 wherein said ink isan aqueous ink containing carbon black.
 21. A method according to claim19 wherein said ink is an aqueous ink containing a mixture of dyesadding up to black.
 22. A method for the preparation of a silk screenprinting element involving the following steps, in order: (1) preparingan ink jet recording material as defined by any of claims 1 to 18, (2)jetting information-wise droplets of an ink onto the front surface ofsaid ink jet recording material by means of an ink jet printer thusforming a printed image, (3) exposing overall by actinic light a silkscreen through a mask consisting of the printed image formed by steps(1) and (2), (4) developing the exposed silk screen into a silk screenprinting element.
 23. A method according to claim 22 wherein said ink isan aqueous ink containing carbon black.
 24. A method according to claim22 wherein said ink is an aqueous ink containing a mixture of dyesadding up to black.